Bar Code Symbology
Bar codes are well known in the art. Today, bar codes are used in just about every type of business application: point-of-sale, retail, warehousing, etc. Bar codes are printed on individual items and on containers enclosing a number of items. Bar codes carry information encoded into bars and spaces of various width, arranged in a predetermined patterns. The bars and spaces are made up of unit elements called modules. A module has a specified height and width. Width is usually called the horizontal dimension of the module. When a bar code is scanned by a laser scanner, bar code modules are usually crossed by the scanning beam along its horizontal dimension. The relative size of a bar coded label is determined by the type of coding used, as are the actual sizes of the label's individual bars and spaces. The size of the bar code is also directly proportional to the amount of information which is stored in that bar code. Conversely, the amount of information is constrained by the size limitations on the bar code. Bar codes usually get scanned via a bar code scanning system, and the encoded information gets extracted and decoded by the system's processing means. Bar code reading can be accomplished by scanning across the bar code with a laser scanner, a charged coupled device (CCD.), or a solid state imaging device(SSI). Bar code reading systems are known in the art and have been disclosed, for example, in U.S. Pat. No. 4,251,798; 4,360,798; 4,369,361; 4,387,297; 4,409,470 and 4,460,120.
A number of different one-dimensional bar code symbologies (encodation schemes) exist. These symbologies include UPC/EAN, Code 39, Code 128, Codabar and Interleaved 2 of 5. Due to their low information density storage capacity these types of bar codes can carry only a limited amount of information, on the order of ten to twenty letters or digits. This information is usually an index to a file or a data base where more comprehensive information is stored.